Many heat exchangers employed in air conditioning or refrigeration systems utilize one or more serpentine conduits on the refrigerant side. In order to prevent the existence of an overly high pressure differential from the vapor inlet to the condensate outlet, which would necessarily require increased energy expenditure in operating the system, the flow passages within such tubes are of relatively large size to avoid high resistance to fluid flow.
As a consequence, the air side of the tubes must be expanded in order to accommodate the relatively large flow passages and this in turn results in a structure wherein a relatively large portion of the frontal area of the air side of the heat exchanger is blocked by the tube with a lesser area available in which air side fins may be disposed to enhance heat transfer.
In order to maintain a desired rate of heat transfer, the air side pressure drop becomes undesirably large and, in turn, results in a commensurately undesirable large system energy requirement in moving the necessary volume of air. To avoid certain of the foregoing problems, it has been proposed to utilize a plurality of parallel tubes extending between between headers with each of the tubes defining a plurality of parallel flow paths within its innards. This allows the use of relatively small individual passages which in turn reduces the percentage of the total frontal area of the device occupied by the tubes.
However, forming tubes to contain a plurality of parallel flow paths has presented a number of difficulties, particularly where the flow paths are intended to have an unusually small hydraulic diameter. Economical extrusion techniques have not yet been developed and where inserts are utilized to subdivide the interior of the tube, difficulty has been met in maintaining the structural integrity of the assemblage to prevent tube rupture at conventional operating pressures as well as to prevent cross flow within the tube between the adjacent flow passages defined by the insert.
The present invention is directed to overcoming one or more of the above problems.